No description available.

The previous cytological and electrophysiological work suggests that the optic tectum matures during metamorphic climax. It was the aim of the present work to attempt to compare pre metamorphic (Stage XII) larval and post metamorphic juvenile, Rana catesbeiana, using a photostimulated evoked electroencephalographic (E.E.G.) response in the optic tectum and correlate that with tissue studies to verify neurophysiological maturation of the optic tectum.

No description available.

It is well established that older adults show a deficit in episodic memory. The associative deficit hypothesis (ADH) (Naveh-Benjamin, 2000) suggests that an age-related reduced ability to create links between units of information is a major contributor to the episodic deficit. It has been a robust finding that older adults show a disproportionate decline in associative memory relative to item memory when compared to young adults. Previous researchers have investigated the role of the frontal lobes (FL) by studying the effect of reduced attentional resources in the associative deficit. However, they have not found that divided attention in young adults produces the disproportionate associative decline seen in aging and it is thought that some cognitive process other than the allocation of attentional resources may contribute to the associative deficit. The present study intended to use a divided attention (DA) task that also engages medial temporal brain regions (MTL) in order to tax additional parts of the network involved in creating associations and provide indirect support for the role of the MTL in the associative deficit. However, the associative memory deficit in older adults was not replicated due to unique poor associative memory performance of some young adults in the study. Analyses excluding these participants show support for the role of the MTL in the associative deficit. However, the young poor performers may provide support for the role of FL function in the associative deficit and show that poor associative memory may not be limited to the older adult cohort.

Thesis (Ph. D.)--University of California, San Diego, 2007. / Title from first page of PDF file (viewed November 7, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.

La simulation des réflexions lumineuses multiples à l'intérieur d'un environnement nécessite de résoudre une intégrale de premier ordre, récursive infinie, pour laquelle il n'existe pas de solution analytique dans le cas général. Certaines méthodes permettent de donner une solution théorique exacte, mais avec des temps de calcul trop important pour espérer produire plusieurs images par seconde dans un avenir proche. De nombreuses méthodes permettent de réaliser ces calculs de manière plus rapide, mais elles reposent sur des approximations dont les effets sont souvent visibles sur les images produites. Notre objectif est de proposer des solutions permettant de réduire les erreurs de calculs en exploitant deux approches complémentaires : (i) une homogénéisation des termes de l'équation de manière à la résoudre seulement à l'aide de quelques opérateurs simples ; (ii) la prise en compte précise des informations de visibilité pour réduire le biais des méthodes reposant sur une estimation de densité. A terme, notre objectif est de diminuer le coût des requêtes de visibilité de nos deux contributions. Pour cela nous envisageons notamment d'introduire des calculs hiérarchiques de visibilité de façon à amortir le coût global des requêtes. / Simulating light transfer within a virtual environment requires to solve a first order, infinite recursive integral, that unfortunately doesn't have any solution in general cases. Though theoretically exact solutions exist, their computing time is not adapted to real-time rendering in a near future. Many methods have been proposed for accelerating these computations, but they rely on approximations that often produce visible artifacts on the resulting images. Our goal is to propose some new solutions that can reduce biases with two complementary approaches : (i) a new homogeneous representation of each term of the equation can be used to resolve it using only simple operators ; (ii) considering precise visibility information in order to reduce bias of methods that rely on density estimation. On the long range, we aim at reducing visibility requests costs of each contribution. For that purpose, we particularly plan to introduce hierarchical visibility computations so as to amortize queries cost.

L’objectif de la présente étude visait à évaluer les effets différentiels de la privation de sommeil (PS) sur le fonctionnement cognitif sous-tendu par les substrats cérébraux distincts, impliqués dans le réseau fronto-pariétal attentionnel, lors de l’administration d’une tâche simple et de courte durée. Les potentiels évoqués cognitifs, avec sites d’enregistrement multiples, ont été prévilégiés afin d’apprécier les effets de la PS sur l’activité cognitive rapide et ses corrélats topographiques. Le matin suivant une PS totale d’une durée de 24 heures et suivant une nuit de sommeil normale, vingt participants ont exécuté une tâche oddball visuelle à 3 stimuli. L’amplitude et la latence ont été analysées pour la P200 et la N200 à titre d’indices frontaux, tandis que la P300 a été analysée, à titre de composante à contribution à la fois frontale et pariétale. Suite à la PS, une augmentation non spécifique de l’amplitude de la P200 frontale à l’hémisphère gauche, ainsi qu’une perte de latéralisation spécifique à la présentation des stimuli cibles, ont été observées. À l’opposé, l’amplitude de la P300 était réduite de façon prédominante dans la région pariétale pour les stimuli cibles. Enfin, un délai de latence non spécifique pour la N200 et la P300, ainsi qu’une atteinte de la performance (temps de réaction ralentis et nombre d’erreurs plus élevé) ont également été objectivées. Les résultats confirment qu’une PS de durée modérée entraîne une altération des processus attentionnels pouvant être objectivée à la fois par les mesures comportementales et électrophysiologiques. Ces modifications sont présentes à toutes les étapes de traitement, tel que démontré par les effets touchant la P200, la N200 et la P300. Qui plus est, la PS affecte différemment les composantes à prédominance frontale et pariétale. / The objective of the present study was to assess the differential effects of sleep deprivation (SD) on cognitive functions relying on distinct cerebral networks, involved in the fronto-parietal attentional network, during a relatively simple and short cognitive task. Multi-sites recording event-related-potentials (ERP) were used in order to evaluate the effect of SD on rapid cognitive activity and its topographical correlates. The morning following a night of total SD and a night of sleep, 20 participants were administered a 3-stimuli visual oddball paradigm. Amplitudes and latencies of the P200 and N200 ERP components were analyzed as frontal indexes, whereas P300 was analyzed as a mixed frontal and parietal component. Following TSD, a non specific increase in P200 amplitude for the left hemisphere, as well as a loss of lateralisation in response to target stimuli, were observed. Contrarily, P300 amplitude was predominantly reduced in the parietal region in response to target stimuli. Moreover, N200 and P300 latencies were delayed non specific to the type of stimuli and performance (reaction time and accuracy) was altered. These results confirm the deleterious effect of a moderate duration SD on attention processes that can be objectified by means of behavioural and electrophysiological measures. Each stages of information processing was altered by SD, as shown by its effect on P2, N2 and P3 components. Moreover, SD affected differently components caracterized by a predominant frontal or parietal distribution.

This study analyzed the relationship between the OF functioning of 100 incarcerated male offenders and their psychopathy symptoms. The study's rejected hypothesis had predicted a significant relationship between measures of OF functioning and the Defective Affective Experience (DAE) and Impulsive and Irresponsible Behavioral Style (IIB) factors of the Cooke and Michie (2001) three-factor model of psychopathy. Regression analysis failed to demonstrate a relationship between OF functioning and the DAE and IIB factors. Group differences on OF functioning were not demonstrated between participants in the upper and lower quartiles of a summed DAE and IIB factor score. A general role for OF functioning in criminal behavior was suggested as two OF measures accounted for 14.9% of the variance of criminal convictions.

No description available.

Thesis (M.A. in Psychology)--Vanderbilt University, Aug. 2001. / Title from title screen. Includes bibliographical references.